Live Case #3

*Frank Diaz M.D. Ph.D., #Negar Khanlou, M.D., and *Perry Shieh, M.D. Ph.D.

*Department of Neurology, #Department of Pathology

UCLA Medical Center

Clinical Presentation• This patient is an 18-year-old right-handed male with a history of high arched

feet, curled toes, and toe walking.

• During the initial visit, he reported his toes catch frequently, resulting in near falls, and uses railing for assistance when climbing stairs. He also reported muscle cramps in both hands.

• He denied swallowing issues, shortness of breath, orthopnea, or double vision

• He denied tingling-like sensations, but did report numbness and pain in his feet in cold weather.

• The family noted toe walking and slower running than his peers starting at 5 years of age.

• At age 13, he started tripping more and developed pain in his feet on ambulation. He underwent bilateral Achilles tendon lengthening surgeries.

• Persistent walking difficulties prompted a new referral to orthopedic surgery.

Review of Systems

Family History

Social History

Additional HistoryPhysical and Neurological Examination

Electrodiagnostic Findings Site Onset (ms) Peak (ms) O-P Amp (µV) Site Dist (cm) Vel (m/s)

Right Median Anti Sensory (2nd Digit)

Wrist 2.6 3.6 36.9 2nd Digit 13.0 50

Right Ulnar Anti Sensory (5th Digit)

Wrist 2.1 3.0 29.0 5th Digit 11.0 52

Site Onset (ms) O-P Amp (mV) Site1 Site2 Dist (cm) Vel (m/s)

Right Median Motor (Abd Poll Brev)

Wrist 4.9 8.5 Elbow Wrist 23.0 51

Elbow 9.4 8.2

Right Peroneal Motor (Ext Dig Brev)

Ankle NR NR

Right Tibial Motor (Abd Hall Brev)

Ankle 9.1 1.0 Knee Ankle

Right Ulnar Motor (Abductor Digit Minimi)

Wrist 3.0 7.7 B Elbow Wrist 22.5 52

B Elbow 7.3 7.6 A Elbow B Elbow 9.0 50

A Elbow 9.1 7.6

Side Muscle Nerve Root Ins

Act

Fibs/P

SW

Fasc Other Amp Dur Poly Recrt

Right AntTibialis Dp Br

Peron

L4-5 Incr 2+ None None Nml Nml Nml Nml

Motor NCSs

Sensory NCSs

EMG

A diagnostic test was performed.

Sural Nerve Biopsy

H&E

Sural Nerve Biopsy: Electron Microscopy (EM)

Methylene Blue EM

Sural Nerve Biopsy: Electron Microscopy

Sural Nerve Biopsy H&E Neurofilament

Genetic Testing

• Two VUS in the GAN (gigaxonin) gene:

• c.1506G>T (p.Trp502Cys) (maternal)

• c.944C>T (p.Pro315Leu) (paternal)

• c.944C>T has been previously reported by Bruno et. al. 2004 and Houlden et. al. 2007

• c.1506G>T has not been reported.

Giant Axonal Neuropathy (GAN)

• In its classic form, it is a severe autosomal recessive disease that affects both the peripheral and central nervous system

• First Described in 1972

• Very rare

• Only about 50 families have been described in the medical literature

• Likely underdiagnosed

Giant Axonal Neuropathy (GAN)

• The gigaxonin gene GAN was identified as the mutated gene in giant axonal neuropathy in 2000 (Bomont et. al. Nat Genet). Located in chromosome 16q24

• Composed of an amino-terminal BTB (for Broad-Complex, Tramtrack and Bric a brac) domain followed by six Kelch repeats

• More than 40 different mutations have been reported.

Giant Axonal Neuropathy (GAN) • E3-ligase adaptor that works as part of the ubiquitin-proteasome system and plays a role in the

breakdown of intermediate filaments

• Loss of GAN causes accumulation of intermediate filaments-> axonal accumulation and axonal swelling

Source. https://neuromuscular.wustl.edu

GIGAXONIN Intermediate Filaments • Neurofilaments• Peripherin• Vimentin• GFAP• Nestin• Desmin• Keratin

Ubiquitin Ligase Complex

Pro

teo

som

e

Giant Axonal Neuropathy (GAN)

Giant Axonal Neuropathy (GAN) • Physical appearance: kinky hair, high forehead, pale complexion, and long

eyelashes

Source. https://blog.timesunion.com

Source. https://globalgenes.org

Source. https://irp.nih.gov

Giant Axonal Neuropathy (GAN): Kinky hair

Our patient’s family

Giant Axonal Neuropathy (GAN) • Physical appearance: red and kinky hair, high forehead, pale complexion, and

long eyelashes

• Symptoms: usually begin before age 5 with gait disturbances and frequent falls due to both weakness and ataxia; numbness is present as well

• CNS involvement: cerebellar dysfunction, spasticity, and optic atrophy; hearing can be affected; intellectual disability, seizures, and dementia can occur

• Autonomic nervous system involvement: neurogenic bladder, constipation, heat intolerance, hypohidrosis or anhidrosis

• Most children become wheelchair dependent in the 2nd decade. Death usually occurs in the 3rd decade most often due to respiratory failure.

Giant Axonal Neuropathy (GAN): Findings

• Imaging Findings: • White matter changes, atrophy

of the cerebellum, and optic tracts

• NCS/EMG: SNAPs are typically absent; motor NCSs can be normal or with amplitude reductions

Demir et. al. J Neurol Neurosurg Psychiatry 2005

Giant Axonal Neuropathy (GAN): Our Patient

Giant Axonal Neuropathy (GAN): Diagnosis

• Diagnosis: Nerve biopsy and genetic testing

Source. https://neuromuscular.wustl.edu

• Nerve Biopsy: Classic findings include axonal loss, giant axon swelling, densely packed bundles of neurofilaments

Giant Axonal Neuropathy (GAN)

What about Treatment?

A Phase I Study of Intrathecal Administration of scAAV9/JeT-GAN for the Treatment of Giant Axonal Neuropathy

• ClinicalTrials.gov Identifier: NCT02362438

• PI: Dr. Carsten Bonnemann

• NIH Clinical Center in Bethesda, MD

• Utilizes an AAV9 vector

• Delivered intrathecally

• Purpose is to primarily target the spinal cord and brainstem motor neurons, as well as the dorsal root ganglion

Bailey et. al. Mol Ther Methods Clin Dev 2018

Acknowledgements

UCLA Neuromuscular Medicine Nasheed JamalPerry ShiehPayam SoltanzadehMelissa Spencer

UCLA Pathology DepartmentNegar Khanlou

Cedars-Sinai Medical Center Neuromuscular Medicine Matthew Burford